To reduce a pressure leakage from a diaphragm by uniting a metallic gasket between a cylinder block and a cylinder head with the diaphragm formed inside the gasket and shifting in accordance with a pressure of a combustion chamber.

A metallic cylinder gasket 1 between a cylinder block 26 and a cylinder head 25 is formed in three layers of a middle plate 10, and an upper seal plate 8 and a lower seal plate 9 holding the middle plate 10 from up and down. A rubber material is applied to the seal plates 8, 9, and a steel material or the like is used for the middle plate 10. A diaphragm 6 of a slightly smaller outer diameter than an inner diameter of an opening part 10B is inserted in the opening part 10B formed in the middle plate 10 of the metallic cylinder gasket 1 to apply a pressure. As a result, a part of the diaphragm 6 fitted to the middle plate 10 is elastically deformed. A material of the diaphragm 6 is supplied to a gap 16 between the diaphragm 6 and opening part 10B of the middle plate, and the diaphragm 6 and middle plate 10 are pressure welded into one body. Accordingly, a pressure leakage from a pressure detection face of the diaphragm 6 can be reduced sufficiently.